Deployment Guide

the export RT associated with the EVI. A receiving VTEP downloads information in the BGP EVPN route to EVIs that have a
matching import RT value.
You can autogenerate or manually configure the RT import and export for each EVI. In auto-EVI mode, RT autogenerates. In
manual EVI configuration mode, you can autogenerate or manually configure the RT.
The RT consists of a 2-octet type and a 6-octet value. If you autoconfigure a RT, the encoding format is different for a 2-byte
and 4-byte AS number (ASN):
● For a 2-byte ASN, the RT type is set to 0200 (Type 0 in RFC 4364). The RT value is encoded in the format that is described
in section 5.1.2.1 of RFC 8365: 2-octet-ASN: 4-octet-number, where the following values are used in the 4-octet-number
field:
○ Type: 1
○
D-ID: 0
○ Service-ID: VNI
● For a 4-byte ASN, the RT type is set to 0202 (Type 2 in RFC 4364). The RT value is encoded in the format: 4-octet-ASN:
2-octet-number, where the 2-octet-number field contains the EVI ID. In auto-EVI mode, the EVI ID is the same as the virtual
network ID (VNID). In 4-byte ASN deployment, OS10 supports RT autoconfiguration if the VNID-to-VNI mapping is the same
on all VTEPs.
NOTE: Dell Technologies recommends using manual route-target for interoperability with network equipment vendors.
Disable RT ASN in BGP EVPN
One of the CLOS Leaf-Spine fabric design with eBGP is to assign separate ASNs to each leaf node and the same ASN to all
spine nodes.
When an overlay using BGP-EVPN as the control-plane is deployed on such a fabric, the leaf acts as the VTEP or EVPN PE
(Provider Edge) node.
This means that EVPN Auto-RT derivation cannot be used as the RT auto-derivation includes the ASN of the PE; as a result, the
RTs derived on each PE will differ from each other.
New Auto-RT Format
The disable-rt-asn mode is a global system level mode that tells the system to use a proprietary format for auto-derived route
targets that deviates from the standard RT auto-derivation.
As this format does not include the ASN of the PE in the RT value, the RTs derived on all PEs with this command are identical
even if they belong to different ASNs.
Applying disable-rt-asn
Whenever the disable-rt-asn command is issued at the system level, the route-targets are re-evaluated and re-applied for
all existing EVIs and VRFs (Symmetric IRB) that are configured to use auto-derived Route-Targets. All EVPN routes are
re-advertised with the new Route-Target. Any Remote MAC addresses or ARPs previously installed based on old EVPN Routes
received with mismatched RTs are removed.
These changes apply to the following modes:
Auto-EVI mode - All EVIs and VRFs.
Manual-EVI mode - All EVIs and VRFs that have auto-rt configured for import or export or both.
When the no disable-rt-asn command is issued, the Route-targets on all EVIs fall-back to the standard based value, all EVPN
routes are re-advertised.
VLT Mismatch
The show vlt mismatch command displays mismatch in the disable-rt-asn mode between the VLT Peers.
Configure BGP EVPN for VXLAN
To set up BGP EVPN service in a VXLAN overlay network:
1. Configure the VXLAN overlay network. If you enable routing for VXLAN virtual networks, Integrated Routing and Bridging
(IRB) for BGP EVPN is automatically enabled. For more information, see Configure VXLAN.
2. Configure BGP to advertise EVPN routes.
BGP EVPN for VXLAN
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